The first thing everyone will ask is, What gauge wire do you have running to your amps?

I have a 4 gauge run going to each amp. I still installed 2 caps the other day. I'm no expert by any means. I just figured that for $80 a piece, what could they hurt? I figured that I probably don't need them most of the time, but they might come in handy when the Batteries start to drain, and they're struggling. Guess we'll see how it goes.

Capacitors are nothing more than a storage device, somewhat like a battery. They are made to discharge all at once. I think if your batteries are very close to the amplifiers they are useless, but that's just my opinion.

bawshogg, This is for my car, not for a boat. I have problems with the headlights dimming when the sub hits. I was looking around on crutchfield and that's what one of the capacitor's description said it was for. I'll have to check what gauge wire I'm running, but the amp that it is being used here is a 600 watt amp if that helps at all.

regardless of what you do, be careful. Capacitors can easily store enough energy to stop your heart even if you have had it disconnected from a battery for a while. Best bet is to do it right and get a good alternator and batter (or more then one battery)

How much power are you running? This sounds like it could be a ground issue. A lot of time a good ground is overlooked but it is just as important as a good power wire. I was only running a 400 watt rms amp in my car and having the same problem. I beefed up my ground wire from the amp to the chassis, added a ground from the battery to the chassis and grounded my deck to the chassis. The wire was much cheaper than a capacitor and fixed the problem completely. If your 100% sure your ground is good and your lights are still dimming check out the BatCaps from Xsatic. I just got one for my boat and it is really bad ass. Basically it is a battery with the speed of a capacitor. The 300 Batcap is equivalent to 100 (1) farad caps.

shadow, it's 12V. That's not gonna stop a heart. Furthermore, extra batteries in cars with moderate systems is a waste because the extra battery is for reserve time, and still draws from the starting battery when the key is on if it's installed right. A capacitor may help in some cases, but a GOOD battery in the car would also help.

All I am trying to say is there is a TON of stuff out there. Do a little research before making a purchase. By the way the batcap 300 is smaller than most capacitors so it would probably save space, if a capacitor is even needed for this application.